Fog blamed for Melbourne flight delays

Fog and low cloud delayed flights from Melbourne Airport as visibility closed in to just 50 metres.

Heavy fog blanketed Melbourne from 3am on Wednesday with some flights delayed by more than half-an-hour while others were diverted.

"We observed visibility at Melbourne Airport down to 50 metres so roughly if you were kicking a goal in the footy you wouldn't be able to see the goal posts from the 50 metre line," senior forecaster Tom Delamotte said.

Low cloud and hazy conditions persisted until early afternoon.

Live flight monitoring sites showed average delays of 34 minutes for flights departing Melbourne at lunchtime, with 68 per cent of flights delayed.

However, earlier data showed passengers were delayed leaving Melbourne by almost an hour with 74 per cent of flights impacted by the heavy fog at 10am.